The three-dimensional structure of a small fungal spindle will be reconstructed from adjacent transverse serial sections, of spindles at different stages of mitosis. This will hopefully indicate whether kinetochore microtubules are significantly associated with microtubules of the continuous spindle, and how 4-fold spindle elongation at anaphase is accomplished. A microbeam will be used to generate small lesions (reduced areas of birefringence) in the central spindle of diatoms, and the effects and behavior of the lesions will be followed by time-lapse and electron-microscopy. The effects of various drugs (cytochalasin, colchicine, DNP, and others) will be followed on both mitotic spindles and selected phenomena involving microtubule-based motility; this and other approaches may help define the nature of such microtubule (and not actin) based systems. New fixation protocols will be investigated using rapid freezing as an initial step; the object is to preserve delicate elements of the motile apparatus of cells which are probably destroyed by conventional fixation protocols.